Theme Drupal based on Role?

Here's my problem: I am using a theme which lets you select from some predefined skins. Some clients want their users to see the site without our branding, so I need to override the skin .css based on role.

I'm not seeing a module that does this, so I come to you! What would be a good way to add a .css file across the site if a user is a specific role?

Thanks!